Messages in this thread | | | Subject | Re: Poor PostgreSQL scaling on Linux 2.6.25-rc5 (vs 2.6.22) | From | "Zhang, Yanmin" <> | Date | Wed, 12 Mar 2008 17:00:55 +0800 |
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On Tue, 2008-03-11 at 16:12 -0700, Nicholas Miell wrote: > On Tue, 2008-03-11 at 22:34 +0100, Cyrus Massoumi wrote: > > Nicholas Miell wrote: > > > > > (Also, ignoring MySQL because it's a terrible piece of software at least > > > when regarding it's scalability is a bad idea. It's the M in LAMP, it > > > has a huge user base, and FreeBSD manages to outperform Linux with the > > > same unscalable piece of software.) > > > > Did you actually see this? > > http://www.kernel.org/pub/linux/kernel/people/npiggin/sysbench/ > > > > FreeBSD does not outperform Linux, it's actually a bit faster according > > to Nick's tests. > > I am aware of those results, but in the mail I was responding to, Nick > Piggin said the following: > > > The problem with MySQL contention means that if the scheduler > > unluckily chooses to deschedule a lock holder, then you can get > > idle time building up on other cores and you can get context switch > > cascades as things all pile up onto this heavily contended lock. As > > such, it means MySQL is not an ideal candidate for looking at > > performance behaviour. I discounted the relatively worse scaling of > > MySQL with 2.6.25-rc (than 2.6.22) as such an effect. > > which I interpreted to mean that MySQL performs worse on 2.6.23+ than on > 2.6.22 but for some reason this doesn't matter. That's because 2.6.23-rc lack the cache hot feature of scheduler. Ingo fixed it in 2.6.24-rc.
-yanmin
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